The present invention relates to a fitting pad for ski boots, and more particularly relates to a fitting pad to be inserted between a skier's foot and a hard shell of a ski boot for painless protection of the foot within the shell.
A shell of a ski boot is made into a relatively hard construction for direct transmission of the movement of the skier's leg to the ski. The size and shape of the foot to be accommodated within the shell differ from skier to skier. For painless, stable holding of a foot within the hard shell of a standardized size and shape regardless of such personal difference in foot size and shape, it is generally employed to place a fitting pad between the foot and the hard shell.
Gum and soft foam urethane have been used for the conventional fitting pad of this kind.
A gum pad is made easily deformable when heated by body temperature of the foot accommodated therein. For such a gum fitting pad is generally used a mixture of low melting point parafin wax with silica, a mixture of natural rubber with cork, a mixture of isobutylene-isoprene copolymer with paper fibers and talc or a mixture of foam styrole with zinc stearate. In use such a gum fitting pad is inserted into the inner boot of a ski boot.
The soft foam urethane fitting pad is formed by mixing two kinds of reactive solutions so that the resultant foaming pressure should inject the pad material into a space between a foot and a shell for subsequent hardening.
As stated above, the gum pad material is made deformable by the body temperature of a foot in direct contact therewith. When used for a long period whilst keeping such a direct thermal contact, accumulation of heat occasionally cause fluidization of the fitting pad which is thereupon rendered vulnerable to force application. As a consequence, continued application of force during long use of the ski boot forces the fitting pad to lose its correct position leading to the problem that movement of the leg cannot be transmitted to the ski sufficiently. In particular in the case of a gum fitting pad containing paraffin wax its highly crystalline nature requires a great deal of melting energy, thereby rendering deformation relatively difficult.
In the case of the soft foam urethane fitting pad, injection of the reactive solutions requires very careful operation. Even a small misstep in the operation would cause loss of balance in the flow of the material and, as a result, a foot in the fitting pad is held at a biased position. In addition, the state of the fitting pad cannot be amended after hardening. Since soft foam urethane is extremely soft, strong pressure must be applied to the foot in covering by the fitting pad and long use of the fitting pad under such a high pressure tends to cause foot pain.